Patients undergoing total hip replacement have a 60-70% incidence of postoperative deep vein thrombosis (DVT). It is not clear at the present time which etiological factors contribute most to the development of DVT in these patients. We have started and will continue a controlled, randomized therapeutic trial to assess the efficacy of low dosage treatment (in an attempt to reduce hypercoagulability) versus intermittent low pressure compression of calves and thighs to combat stasis and will compare the results obtained with these two treatment group with those of a control group. Patients are injected with I125- fibrinogen prior to surgery and their legs are scanned at least every second day to determine if fibrinogen localizes in the form of fibrin deposits over any particular area. Patients exhibiting suspect rises of radioactive counts will be subjected to venography for confirmation or absence of DVT. Studies will be undertaken to determine if sequentially performed blood coagulation assays have any value to predict the development of DVT in patients at high risk, followed with I125- fibrinogen scanning.